sedimentary

Weathered sandstone or quartzite cobble

Quartz-rich sandstone; possibly metamorphosed to quartzite

AI-generated identification · may be incorrect

Fine-grained, brown to gray, dull-to-satin luster, with rounded weathered surfaces and no obvious crystals or cleavage. Likely Mohs hardness 6–7 if quartz-rich; exact identification requires a fresh break, hand lens, and acid test.

Identified September 13, 2026More sedimentary →

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Physical properties

Formation & geological history

Sand-sized quartz and rock fragments were lithified in an ancient sedimentary basin; if quartzite, later burial and metamorphism fused the grains. Geological age cannot be determined from the photograph.

Uses & applications

Common sandstone is used for building stone, paving, aggregate, and decorative pieces; quartzite is used for countertops, construction aggregate, and landscaping. This rounded specimen has little commercial value unless unusually attractive or provenance is known.

Geological facts

The granular texture and muted iron-stained coloration suggest a quartz-rich clastic rock, but the image alone cannot reliably distinguish sandstone from quartzite.

Field identification & locations

Look for visible sand grains and pores in sandstone, versus tightly interlocked grains and conchoidal fracture in quartzite; quartz-rich material should resist a steel knife and scratch glass. Common worldwide in riverbeds, beaches, and outcrops.